Push button actuator



April 7, 1959 J. WALKER 2,881,402

` PUSH BUTTON ACTUATOR Filed neo. a, 1955 IN V EN TOR. JMEs/QMLKER BY C',

Y TTOENE Y nited States Patent PUSH BUTTON ACTUATOR James R. Walker, Detroit, Mich., assignor to Gordon H. Cork, Birmingham, Mich.

Application December 8, 1955, Serial No. 551,754 Claims. (Cl. 336-136) This invention relates to a comparatively low voltage push button operated relay or actuator for supplying an electrical actuating stimulus, as for example an electrical potential signal or stimulus suitable for actuating a transistor or grid controlled vacuum tube.

An object of the invention is to provide an improved push button actuator of the above character which is of particularly rugged and simple construction susceptible to economical manufacture by mass production methods, yet which is eicient in operation and effects a sharp potential signal or stimulus adjacent the end of the push button movement.

Another object is to provide such an actuator which is readily and feasibly assembled from metal stampings and molded or screw machine parts.

Another object is to provide such an actuator comprising primary and secondary coils wound around an annular bobbin supported within a housing. A thin sheet iron or soft steel plate or wafer adjacent one end of the bobbin is provided with a hole therethrough coaxial with the bore of the bobbin. A guide plunger of aluminum or other suitable non-magnetizable material having an enlarged outer end of larger diameter than the diameter of the hole through the wafer, so as to block passage therethrough, extends axially through the latter hole and approximately two-thirds of the way through the bore of the bobbin. Secured coaxially to the inner end of the non-magnetizable guide plunger is a magnetizable core plunger, preferably of soft iron or steel, having the same diameter as the guide plunger and extending outwardly therefrom to an enlarged push button end. Spring means yieldingly urge the push button end of the iron core plunger outwardly to the limit of movement permitted by abutment between the enlarged head of the guide plunger and fixed portions of the actuator assembly.

By virtue of this construction, the wafer and bobbin are feasibly assembled comparatively loosely within the housing. Dimensional tolerances of the holes or bores through the bobbin and wafer need not be maintained closely because the push button movement of the iron core plunger into the hole of the wafer is guided by the non-magnetizable guide plunger. During the plunger movement, the voltage of the secondary coil rises slowly from a nominal Value until the iron core plunger closely approaches the iron wafer. Thereafter upon continued movement of the iron core plunger into the hole in the wafer, the secondary voltage rises rapidly to its desired optimum actuating potential.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

Fig. l is a plan view of push button relay embodying the present invention.

Fig. 2 is a vertical mid-sectional view taken in the direction of the arrows substantially along the line 2 2 of Fig. 1.

Fig. 3 illustrates the change in secondary coil potential es with respect to inward movement of the plunger.

Fig. 4 is a view similar to Fig. 2 illustrating a modification of the present invention.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments: and of being practiced or carried out in various ways.. Also it is to be understood that the phraseology or termi-- nology employed herein is for the purpose of description and not of limitation.

Referring to the drawings, a push button actuated relay is illustrated by way of example comprising a two-part housing of non-magnetizable material such as aluminum or plastic. In the present instance the housing includes a base portion 10 and a retaining collar 12, both being of square horizontal cross section. The portion 10 is provided with a large central cylindrical bore 14 terminating at its lower end in a bore portion 16 of reduced diameter, thereby to provide an annular bottom ilange 10a integral with the portion 10. A thin annular wafer or plate 17 of magnetizable material, such as soft iron or steel, is supported on the flange 10a substantially coaxially with the bore 16. Supported on the wafer 17 is an annular bobbin or coil form 18 of suitable thin dielectric material having the windings of primary and secondary coils thereon indicated generally by the nu meral 20.

In the present instance the bobbin comprises a vertical cylindrical portion 18a coaxial with the bore 16 and having upper and lower llanges 18b and 18C respectively extending outwardly substantially to the cylindrical wall of the bore 14. The inner diameters of the bobbin 18 and wafer 17 are substantially the same as the inner diameter of the bore portion 16. The paired leads 22 and 24 for the primary and secondary windings respectively extend through an opening 26 in the housing 10 for connection with suitable terminals or binding posts on the housing, or, in the case of the secondary leads, are connected to a suitable rectifier where a D. C. actuating signal is desired.

The central bore 14 enlarges upwardly to provide an opening 30 for the collar 12, the latter being suitably secured to the base 10 by lscrews 28. The collar 12 is provided with a lower central bore 32 substantially equal to the diameter of the bore 16 and coaxial therewith. Upwardly the bore 32 enlarges at 34 to provide an annular space for a coil spring 36 under compression between the collar 12 and the enlarged head or push button end 38 of a readily magnetizable soft iron plunger core 40. The latter is integral with the head 38 and extends axially through the spring 36, bore 12, and into the bore of the bobbin 18 to fit closely therein. Extending coaxially from the lower end of the plunger 40 and secured thereto is a plunger or guide 42 of the aforesaid nonmagnetizable material having the same diameter as the plunger 40. In the present instance the guide plunger is provided with an integral threaded upper tip 44 screwed into the plunger 40. The lower end of the guide plunger 42 is provided with an enlarged flange 46 adapted to seat against the outer surface of the base 10a.

The plate or wafer 17 is approximately one-sixteenth of an inch thick and closely encircles the plunger 42 which is freely slidable therethrough. In the normal rest position, the lower end of plunger 46 extends downwardly into the windings 20 approximately one-third of the latters axial dimension. Spring 36 is dimensioned with respect to the axial dimension of the aforesaid annularnspace in the boreenlargement 34' so as toallow approximately one-fourth-to three-eighths.V ofan-inchVY downward travel of plunger 40, at which point the latters lower end will Vbe a few thousandths of an inch below the upper'surfacefoffthewafer'lf I'andthe coil'slof' spring 36 will be compressed tightly togethentof-fstop" further downward travel;

The relay device shown is particularly suitablev for' use at` comparatively ylow voltagesY ofthe order'of magnitude of approximately l volts applied tothe primary windings, whereby an optimum output voltage'of the secondarywindings -whenplunger '40 4isat its lowermost posi-1 tionwill -rbe 'approximately 5`V`olts' as SaV resultof circuit losses. Whenthe plunger 49' is at its vupper rest positionA shown, the secondary potential will beat a nominal yvalue? inthe neighborhood of approximately one-tenth of a volt.

In l operation of the actuator; thefpri'mary windings are energized and the head or push button 3S is depressedagainst/the tension of spring .36' to the limit ofdownward. movement.

20,:the secondary outputL potential will remain substan# tially at its aforesaid nominal value throughout the major extent of downward plunger movement. During this movement, the air gap betweenplunger 4G and wafer 17 comprises a high vresistanceto the magnetic iiux circuit,

theiinward plunger movement increases to the right. For' more than tWo-thirds-of the plunger movement, the in# crease in secondary voltage from the nominal potentialy eo is so slight that, when the applied primary potentialis approximately l5 volts, the resulting secondary voltage will vbe insuflicient to transmit direct `current through the usual commercial rectifier. However afterfth'e'lower end of'plunger 40 approaches' to within a few thousandths of an inch of the upper surface of the plate 17, the secondary vvoltage es'rises rapidly as illustrated to its optimum value upon continued inward movement of said lower end to a location a few thousandths of an inch below the upper surfaceof the wafer 17. Thus aV critical actuating potential change is effected in the secondary voltage suitable for use as a control stimulus, as for example to be applied between the emitterk and base of -a transistor to cause a sharp rise in the latters collector current.

It is valso apparent that by virtue of the equal diameters of the plungers 40 and 42, the effect of a unitary plunger .is achieved and the lower end of the iron core plunger 40 is guided directly into the hole in the wafer' tor'a position below the upper surface of the latter. Also in accordance with the construction shown, a'numberof similar actuator assemblies can be secured together'in tandem with the aluminum head 46 of each actuator in juxtaposition with the push button end 3S'of the next' adjacent actuator. Accordingly upon depressing the endmost push button 38, the head 46 of the attached lguide plunger 42 will depress the push button end 38 of the next successive plunger, and so onto the end` of the chain.`

A' modification of the present invention is illustrated' in Fig. 4 wherein the plungers 40 .and 4?., windings Ztl;`

bobbin 18 and coil spring 36 are assembled together substantially as described above.

the-.wafer 17. The bobbin 18 containing Ythe'vwindings' 20Ytswithin theshell 50 and is supported on'the baseplateSOa. Overlying the shell 570 Vvisa closure-Sfrse'eured to an annular inbent lupperffflange' 5% of 'ariel-shell 50T By vvirtue of the constructionshow'n comprising the plate 17 adjacent and below the windings" In this instance however,A instead of the housing 10, 12, a two-part housing Sli, 51

4. by" screws 52.' A spacer 51a extending downwardly around-thecore-.plunger 40-terminates in a radially -outwardly extending ange 51b overlying the upper surface of the bobbin 18 so as to hold the bottom of the latter adjacent the magnetizable base plate 59a. As before, the unitary plunger comprising the iron core 40 and aluminum guide portion 42 extends through the central bore of the bobbin 18 and coaxial openings in the base a and closureSl. In this instance, thej-coil spring 36 is under compression between the head 38 and upper end of the bobbi'n`18'-andyieldingly holds the enlargement 46 upwardly against the-`underside ofthe plate 50a. Also in'this instance, the 1eads-22 of the primary windings are shown connected to kbinding posts 53 suitably secured to and suitablyUinsulated 'from the sides of the shell 50 and extending outwardly therefrom. Similarly the leads from the secondary windings 24 are secured to binding posts S4 suitably secured to, suitably insulated from, .andXextendingoutwardly' from the lshellSO The operation of 'thestru'cture of Fig. 4 andthe rei' lation'ship between the secondarvoutput potential and 'tl-lev plunger-movement are substantially the same as described above in regard 4to Pigs. l and 2. Although the' outer shell 50fcomprisesia -magnetizable material,` it has no'appreciable etecton the operating characteristics of the actuator assembly, which is apparentlyrdeterf mined primarily"by the extent of theair gap between" the lower end of plunger 407 and base plate 50a.

I claim.

1. In a push button actuator assembly adaptedito" supply a 'sharp electrical` potential stimulus, a coil form having'a hollow core, primary and secondary 'coilwindf ings around said form, a thin plate of magnetizable mat'erial having an inner surface in juxtaposition with oneend of saidform and `having `a hole aligned with said core, a'` plunger extending'slidably through said core and hole," said plunger comprising a non-magnetizable portion and a magnetizable portion of equal diameters and connected together coaxially in end-to-end alignment for endwise shifting in`unison, the non-magnetizable portion extending entirely through said hole and into said core to said magnetizable portion at a position of low inductive'coupling between saidwindings and being shiftable in oneA direction from said core until the connected end ofv said magnetizable portion is within said hole'and between the Ainner and outer surfaces-of 'said plate at a positionV of high inductive coupling between said windings, interengage'able 'movement limiting means ron said plunger'v and portions of said assembly vfixed with respect Vto said form for limiting movement of said plunger in said direction beyond said position ofV high inductive coupling and for limiting movement ofsaidplunger oppositely to said direction beyond said-position of low inductive coupling,v

and resilient means engaging said plunger and aportion of'said assembly xed'with respect to said formkv yieldingly urging said plunger oppositely to said direction.

2. In a push button actuator adapted to supply a sharp electrical potential stimulus, a coil form having a hollow core, primary and secondary coil winding around said core, a thin plate of magnetizable material adjacent one f1 end of said core and perpendicular thereto, saidplate` having a hole'therethrough aligned with said core,A a'- connected coaxially in end-to-end alignment, said guideportion extending from an inner end within said core through said hole and an openingl in said housingand terminating outwardly of the latter in an enlarged movement limiting end abutting said housing, said magnetizable portion extending from said inner end through an opening in said housing and terminating inlanjenl'arged pusli button'- outwardly of"'said"housiug,' spring means interposed between portions of said housing and pushbutton and yielding urging the latter outwardly to hold said movement limiting end yieldingly in abutment with said housing, and movement limiting means cooperable with said push button for limiting inward movement thereof to a position whereat the inner end of said magnetizable portion is within said hole.

3. In a push button actuator adapted to supply a sharp electrical potential stimulus, a coil form having a hollow core, primary and secondary coil winding around said core, a thin plate of magnetizable material adjacent one end of said core and perpendicular thereto, said plate having a hole therethrough aligned with said core, a housing enclosing said form and having sidewalls connected to and extending from the edges of said plate, means within said housing holding said form adjacent said plate, a plunger of uniform circumference substantially filling said core and comprising a magnetizable portion and a non-magnetizable guide portion connected coaxially in end-to-end alignment, said guide portion extending from an inner end within said core through said hole and terminating outwardly of the latter in an enlarged movement limiting end abutting said plate, said magnetizable portion extending from said inner end through an opening in said housing and terminating in an enlarged push button outwardly of said housing, spring means engaging said push-button under tension yieldingly urging the latter outwardly to hold said movement limiting end yieldingly in abutment with said plate, and movement limiting means cooperable with said push button for limiting inward movement thereof to a position whereat the inner end of said magnetizable portion is within said hole.

4. In a push button actuator adapted to supply a sharp electrical potential stimulus, a coil form having a hollow core, primary and secondary coil winding around said core, a thin plate of magnetizable material adjacent one end of said core and perpendicular thereto, said plate having a hole therethrough aligned with said core, a housing enclosing said form and having sidewalls connected to and extending from the edges of said plate, means within said housing holding said form adjacent said plate, a plunger of uniform circumference substantially illing said core and comprising a magnetizable 5 2,430,757

portion and a non-magnetizable guide portion connected coaxially in end-to-end alignment, said guide portion extending from an inner end within said core through said hole and terminating outwardly of the latter in an enlarged movement limiting end abutting said plate, said magnetizable portion extending from said inner end through an opening in said housing and terminating in an enlarged push button outwardly of said housing, spring means under tension between said push-button and form yieldingly urging said push-button outwardly to hold said movement limiting end yieldingly in abutment with said plate, and movement limiting means cooperable with said push button for limiting inward movement thereof to a position whereat the inner end of said magnetizable portion is within said hole.

5. In a push button actuator adapted to supply a sharp electrical potential stimulus, a coil form having a hollow core, primary and secondary coil windings around said form, a magnetizable material adjacent one end of said form and having a hole aligned with said core, a plunger extending slidably through said core and said hole, said plunger comprising a non-magnetizable portion and a magnetizable portion connected in end-to-end alignment for endwise shifting in unison, the non-magnetizable portion in the non-actuating position of the plunger extending entirely through said hole and into said core to provide a relatively substantial spacing between said magnetizable portion of the plunger and said magnetizable material and consequently providing a low inductive coupling between said windings, said plunger being shiftable through positions of continued relatively low inductive coupling to an actuating position wherein said magnetizable portion of the plunger and said magnetizable material are adjacent each other and consequently provide a high inductive coupling between said windings, and said plunger being limited in its movement toward the actuating position substantially to that point where one end of said magnetizable portion has entered said hole.

References Cited in the tile of this patent UNITED STATES PATENTS Van Loon Aug. 27, 1946 Conrad Nov. 11, 1947 

